Spin-gap formation due to spin-Peierls instability in -orbital-ordered

Mizuki Miyajima, Fahmi Astuti, Takahito Fukuda, Masashi Kodani, Shinsuke Iida, Shinichiro Asai, Akira Matsuo, Takatsugu Masuda, Koichi Kindo, Takumi Hasegawa, Tatsuo C. Kobayashi, Takehito Nakano, Isao Watanabe, Takashi Kambe

Research output: Contribution to journalArticlepeer-review

Abstract

We have investigated the low-temperature magnetism of sodium superoxide (), in which spin, orbital, and lattice degrees of freedom are closely entangled. The magnetic susceptibility shows anomalies at  K and  K, which correspond well to the structural phase transition temperatures, and a sudden decrease below  K. At 4.2 K, the magnetization shows a clear stepwise anomaly around 30 T with a large hysteresis. In addition, the muon spin relaxation experiments indicate no magnetic phase transition down to  K. The inelastic neutron scattering spectrum exhibits magnetic excitation with a finite energy gap. These results confirm that the ground state of is a spin-singlet state. To understand this ground state in , we performed Raman scattering experiments. All the Raman-active libration modes expected for the marcasite phase below are observed. Furthermore, we find that several new peaks appear below . This directly evidences the low crystal symmetry, namely, the presence of the phase transition at . We conclude that the singlet ground state of is due to the spin-Peierls instability.

Original languageEnglish
Article numberL140402
JournalPhysical Review B
Volume104
Issue number14
DOIs
Publication statusPublished - Oct 1 2021

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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